This section is intended to provide information relevant to understanding various technologies described herein. As the section's title implies, this is a discussion of related art that should in no way imply that it is prior art. Generally, related art may or may not be considered prior art. It should therefore be understood that any statement in this section should be read in this light, and not as any admission of prior art.
Generally, electronic designers employ various techniques to design integrated circuits, such as physical chips and/or physical layers. In some situations, at advanced lithography nodes (where images being printed are smaller than the wavelength of light being used), it may be necessary that shapes on a given layer are aligned. Because of these shapes being printed smaller than the wavelength of light being used for the lithography, diffraction of the light being used becomes a significant problem.
A common solution to deal with diffraction is that some sort of a pattern of shapes and spaces is defined such that the shapes are printed successfully. Such a pattern may be comprised of a constant minimum width shape, w, and a constant space, s, that is repeated on a pitch, p, of p=w+s. This is only one such pattern. All the shapes on this layer may then be constructed with this repeating pitch. A lithographic structure is created with such a pattern on any given layer. If two lithographic structures are then placed adjacent to each other, they should be aligned such that the diffraction pattern created by the second lithographic structure is aligned to the first lithographic structure so that no destructive interference occurs.
This alignment becomes much more difficult where there are multiple layers within a lithographic structure which use different pitches. If there are two different pitches on the two different layers, then the alignment between the two lithographic structures is typically resolved on a least common multiple between the two pitches on the two separate layers. However, as more layers are added with different pitches (or pattern requirements), then the solution of using a least common multiple becomes increasingly difficult to solve. It may result in significant spaces between such structures such that there results in a loss of density. Thus, there is a need for allowing a reasonable minimum space to be used between these two structures.